The invention relates generally to journal bearings, and more particularly to self-aligning and self-lubricating journal bearings of simple construction.
Inexpensive bearings for light machinery, for example, the rotor shaft of a fractional horsepower electric motor, must be capable of efficient mass production while conforming to relatively rigid tolerances and long useful lifetimes. During manufacture of a self-lubricating bearing, a fluent, oil-impregnated, fibrous wicking material is injected into the cavity surrounding a porous bearing of sintered metal through which the oil penetrates to reach a shaft jounaled for rotation in a bore in the bearing. A self-aligning bearing of the self-lubricating type has a truncated spherical, bead-shaped porous bearing which is received for limited universal movement in a socket formed by a casing. In the past, the two sides of the casing itself have contacted opposite spherical surfaces of the bearing to complete the "ball and socket" arrangement with enough friction to prevent the bearing from rotating with the shaft while enabling pre-alignment of the axis of the bearing within the casing with the axis of the shaft to be journaled therein.
One of the production problems in manufacturing a self-lubricating, self-aligning bearing of this general type is "quality control" of the degree of tightness of the bearing in the socket. Another problem is to insure that the two elements which form the bearing socket are precisely concentric. Moreover, if the bearing is to fit in a mounting hole in the end bell of a motor, for example, the geometric center of the spherical bearing should lie on the axis of the mounting hole. This is known as the requirement for "concentricity." Slight deviations from concentricity can have a drastic effect on the way in which the bearing wears with use and thus can reduce its average useful lifetime and/or make the lifetime too unpredictable.